This invention relates to an improved system and method for restraining cargo during transportation. More particularly, this invention relates to a novel system and method for securing and restraining undesired movement of boxes, palletized or not palletized, drums, and the like within the interior of an intermodal container in ship cargo holds, placed on flatbed truck trailers, on railroad flatcars, and the like.
Most shipments for export, both in the United States and abroad, are placed into either twenty or forty foot long, rectangular, intermodal containers. These containers are fabricated with steel, corrugated sidewalls and are structurally self-supporting and rugged. Several intermodal containers may be stacked on top of each other for transport by sea, rail, or road. Within the containers, drums or boxes hold actual product. The cargo of these intermodal containers experiences various forces throughout the course of transport.
When traveling by rail, flatbed rail cars transporting intermodal containers may be made up through a process called humping. In this process, a flatbed rail car is pushed over an elevated section of tracks and then allowed to roll into a switching yard, where the cars are switched to make up train segments. When a car is rolled into a stationary string of cars, the impact causes the couplings to lock together. This impact, however, can also apply a force to the cargo of the magnitude of several times the force of gravity. Moreover, during transport, cars are subject to sudden braking forces, run-in and run-out impact over grades, rail vibration, dips in the track, and swaying. When intermodal containers are transported by sea, the cargo therein is subjected to rolling storm forces including: yaw, pitch, heave, sway, and surge. On the highway, intermodal containers and the cargo therein experiences acceleration and centrifugal loads, sudden braking, and vibration. Each of these forces has the potential to impart a substantial force on an intermodal container.
During transportation, an intermodal container and its cargo are two separate entities for the purposes of motion. The container may be mounted in a ship's cargo hold, on a flatbed railcar, on a flatbed truck trailer, or the like. The cargo, however, unless secured to the container is free to move within the interior of the intermodal container.
When the container changes direction or speed, the cargo tends to continue along the previously existing path until it contacts an interior wall of the container. Without some type of restraint and/or cushioning system, the cargo builds up considerable momentum, independent of the container. The amount of momentum is equal to the object's mass multiplied by its velocity. In the case of large cargo loads, even the slightest change in direction, or velocity, can generate substantial momentum. When cargo contacts the interior walls or doors of the container, the force necessary to reduce this momentum to zero is absorbed by the goods. Such forces may result in damage to the cargo, damage to the interior walls or doors of the container, damage to the cargo packaging, and may create dangerous leaks if the cargo is a hazardous material. Accordingly, it is undesirable to permit cargo to gain any momentum independent of the container. This is accomplished by restraining the cargo within the container so that the cargo and the container are essentially united during transport and operationally functioning as one object.
Accordingly, in the past, lading has been secured in the container to eliminate unwanted movement or shifting during transport. The drums, boxes, or other containers have been restrained in several different ways. Primarily, cargo was stabilized by a method of load-locking and lumber bracing. This system involves strategically placing lumber between a loadface and the rear doors of a container. This, however, can be a costly, time consuming, and generally inefficient means of securing a load. In this, the blocking process requires carpenters and is often outsourced to contractors. Accordingly, wood barriers can be time consuming to install and not very cost effective. Still further, wood bracing can be somewhat brittle and subject to failure under an abrupt impact. Moreover, conventional methods of load-locking and lumber bracing simply could not perform some tasks. For example, the most efficient means of filling an intermodal container is eighty fifty-five gallon drums double stacked in a twenty-foot long container. If this is done, however, there are only approximately one to two inches between the loadface and the rear doors. One to two inches is not enough space to put sufficient lumber to brace a load of eighty drums adequately. Consequently, when wood bracing was utilized as a system of restraint, shippers were forced to ship containers that were not filled to capacity, thereby reducing transport efficiency and increasing transportation costs.
Similarly, the Bureau of Explosives has established a standard of review to determine if a particular restraint system is capable of adequately securing hazardous cargo. In certain instances, conventional load-locking and lumber bracing was not able to receive approval to ship hazardous cargo by the Bureau.
Other known means of restraint employed ropes, straps, or stands. Methods appearing in the past have tended to exhibit impaired performance and are often not functionally suitable to restrain loads under even moderate conditions. Consequently, a need exists for securing lading in intermodal containers that is functionally effective, cost-efficient, labor-efficient, and able to comply with Department of Transportation and Bureau of Explosives regulations.
At least one method and apparatus for restraining cargo movement which overcomes some of the foregoing limitations is disclosed in U.S. Pat. No. 4,264,251, of common assignment with the subject application. The invention disclosed in that patent comprises sealing strips that are adhered to opposing sidewalls of a container, a strip of bracing material, and an adjoining mechanism used to bind the ends of the strips together into a secure and taut restraint. The disclosure of this patent is hereby incorporated by reference as though set forth at length. Thus, the concept of a strip of material being used as a barrier to restrain cargo or lading is disclosed in the '251 patent.
In the '251 patent, material strips were applied in a manner similar to hanging wallpaper, wherein a separate adhesive was applied to the surface where adhesion was desired. Then the retaining strip was applied. In addition to this requirement of a separate adhesive, the systems in the past had problems with weakness at the joints. At the juncture where the strips came together, an opportunity existed for slippage of the joined panels. Moreover, intermodal containers have corrugated walls. These corrugations make applying a restraining strip to a separate adhesive, which may not have an even application, substantially more difficult.
Restraining systems in the past required multiple elements, were difficult to store, were arduous to install, and often required a degree of skilled labor. Systems using straps, nails, anchors, or bolts all require substantial storage space even when not in use. Furthermore, such systems increase the safety risk to the workers restraining the cargo.
Still further, products and procedures used in the past relying on accessories located in the cargo container often were not able to secure a partial load. That is, if the load does not extend to the far rear of the container, the necessary anchors may not be available in an area where they can be used.
The problems suggested in the foregoing are not intended to be exhaustive but rather are among many which may tend to reduce the effectiveness of cargo restraining systems. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that cargo-restraining systems appearing in the prior art have not been altogether satisfactory.